[PATCH v3 01/12] tracing: Add trace_array_find/_get() to find instance trace arrays

From: Tom Zanussi
Date: Fri Jan 24 2020 - 17:56:37 EST


Add a new trace_array_find() function that can be used to find a trace
array given the instance name, and replace existing code that does the
same thing with it. Also add trace_array_find_get() which does the
same but returns the trace array after upping its refcount.

Also make both available for use outside of trace.c.

Signed-off-by: Tom Zanussi <zanussi@xxxxxxxxxx>
---
kernel/trace/trace.c | 43 +++++++++++++++++++++++++++++++++----------
kernel/trace/trace.h | 2 ++
2 files changed, 35 insertions(+), 10 deletions(-)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index d1410b4462ac..2d4b70bd85a2 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -8501,6 +8501,34 @@ static void update_tracer_options(struct trace_array *tr)
mutex_unlock(&trace_types_lock);
}

+/* Must have trace_types_lock held */
+struct trace_array *trace_array_find(const char *instance)
+{
+ struct trace_array *tr, *found = NULL;
+
+ list_for_each_entry(tr, &ftrace_trace_arrays, list) {
+ if (tr->name && strcmp(tr->name, instance) == 0) {
+ found = tr;
+ break;
+ }
+ }
+
+ return found;
+}
+
+struct trace_array *trace_array_find_get(const char *instance)
+{
+ struct trace_array *tr;
+
+ mutex_lock(&trace_types_lock);
+ tr = trace_array_find(instance);
+ if (tr)
+ tr->ref++;
+ mutex_unlock(&trace_types_lock);
+
+ return tr;
+}
+
static struct trace_array *trace_array_create(const char *name)
{
struct trace_array *tr;
@@ -8577,10 +8605,8 @@ static int instance_mkdir(const char *name)
mutex_lock(&trace_types_lock);

ret = -EEXIST;
- list_for_each_entry(tr, &ftrace_trace_arrays, list) {
- if (tr->name && strcmp(tr->name, name) == 0)
- goto out_unlock;
- }
+ if (trace_array_find(name))
+ goto out_unlock;

tr = trace_array_create(name);

@@ -8704,12 +8730,9 @@ static int instance_rmdir(const char *name)
mutex_lock(&trace_types_lock);

ret = -ENODEV;
- list_for_each_entry(tr, &ftrace_trace_arrays, list) {
- if (tr->name && strcmp(tr->name, name) == 0) {
- ret = __remove_instance(tr);
- break;
- }
- }
+ tr = trace_array_find(name);
+ if (tr)
+ ret = __remove_instance(tr);

mutex_unlock(&trace_types_lock);
mutex_unlock(&event_mutex);
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 4812a36affac..8fe3b16c8cec 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -346,6 +346,8 @@ extern struct mutex trace_types_lock;

extern int trace_array_get(struct trace_array *tr);
extern int tracing_check_open_get_tr(struct trace_array *tr);
+extern struct trace_array *trace_array_find(const char *instance);
+extern struct trace_array *trace_array_find_get(const char *instance);

extern int tracing_set_time_stamp_abs(struct trace_array *tr, bool abs);
extern int tracing_set_clock(struct trace_array *tr, const char *clockstr);
--
2.14.1